Acoustic amplifier and radiator



July/Z24, 192s.

2 Sheets-Sheet Filed Dec. 24, 1926,

July 24, 1928. 1,678,214

E. A. GRAHAM ACOUSTIC AMPLIFIER AND RADIATOR Filed Dec. 24, 1926 2Sheets-Sheet 2 lkventor' rial No. 97,130, filed by E Patented July 24,1928.

NIT'EID STA -s EDWARD (GRAHAM, DECEASED, LATE vBROCKJLZEY, EGND'ON;ENGLAETD, .BY

.MABIAGR'AHJAM, .EXECUTRIX, OF BECKE'NHA'M, I ENGLAND, AND ALFREDGRAHAM,

EXEGUTOR, OF .FO-REST HILL, .LONDON, ENGLAND, ASS IGNORS 0 GRAHAMAMPIJIOEN LIMITED, "OF LONDON, ENGLAND.

ACOUSTIC .AMPLIFIER AND nA-nrjiron.

Application.filednecember'24, 1926,.Seria1 No. 156,967, and rnGreatBritain February 20, 1926. U I

In the specification of an a i plication Secl -ward Alfred Graham, ofwhom we are executors, for Letters Patent, there "is described aninvention having for its ob ject to provide an1mproved acousticamplifier and radiator f v p v k v bodied, if so de's1 red, 1n a cab net01' other.

a so

which shall be suitable for use with apparatus in which sound waves areproduced or originated by the vibration of a diaphragm,

as in the case of an electro-magnetic telephonic receiver, or the soundbox of agramophone, whichshallfbe compact in form, suit- .able .forembodying in a cabinet or casing,

and highly efiicientin use, quality of tone being maintained, togetherwith maximum volume. i v

The invention as described in the said prior specification, 'ischaracterized in that the sound amplifying and radiating means adaptedto co-actwith a sound directing conduit, comprises multiple concavereflecting surfaces one of which is of comparatively large curvature andblends into another which is of comparatively small curvature, thearrangement being such that sound waves projected on to such anamplifier will be radiated therefrom and diffused through the outletorifice of such acoustic amplifier and radiator.

Now the present invention is an improvement in or modification of theinvention claimed in the .said'ear'lier specification, the

improvement or modification consisting in this that although multiplereflecting surfaces are employed, they comprise a concave surface andone or more flat surfaces, the single flat surface, or one at least ofsuch flatsurfaces when several are used, being inclined to the outletorifice of the acoustic amplifier and radiator.

Thus, the acoustic amplifier and radiator comprises a reflecting elementhaving .a concave reflecting surface and one or more flat secondaryreflectingsurtaces such as referred to, and a sound wave developingconduit, the concave reflecting surface and sound conduit being soarranged :in relation to eachother and to the flat reflecting surface orsurfaces that sound "impinging on the concave surface will be reflectedtherefrom and thence be radiated and diff-used through the out letorifice of the acoustic amplifier and radiatorby the flat reflectingsurface or surfaces. 5

Such a combination ofrefiecting surfaces can be constructed in numerousways, each amplifier iandradiator according to the pre sent invention.Fig. :2 shows the acoustic amplifier and radiator in front elevation,the upper portion of the cabinet being raised for the purpose. Fig. .3is a horizontal section on the line III-{III of-Fig. 1. Figs. 4,5, 6;

and I? are horizontal sections-showing modified constructions. F1gsm8and 9Lareperspect1ve views showing iturther modifications.

Fig. "10 shows in front elevation a still ,tu'rthermodification. F gs.1,.2and 3 show one example of an acoustic amplifier and radiatoraccording to the invention, particularly applicable :as. a

sound .amplifyingaud radiating chamber for a loud speaking telephone. Itconsists ot a v :trough orscoop-like :structure comprising a verticallyarranged reflectin element 1 havinga concave reflecting .suriace(hereinfatter calle dflthe concave reflector) a vertically arranged flatreflecting surface 4- {hereinatter called the fiat reflector)constituted by a w a ll inclined to the axis vor theconcave reflector 2and to the outletorificie, A of the structure, a vertical rear wall 5connecting the rearends oi the concave and flat .reflectors l and at andarranged parallel to the outlet orifice of the, structure and. which may-.or may not act as a reflector, and top andbottom walls 6 and? whichextendover, and

4: and rear wall 5. The refie ctorl which, in horizontalnsection is ofparabolic shape, is adapted to coact with a soundwavedeveloping conduit2 that is of gradually .in-

under .the concavelandnfiat reflectors l and.

creasingcross sectional area and carriescat:

its constricted end,,.a telephonic receiving unit 3. The sound conduit.2, which in this exampleis straight and arranged with its axis coaxialwith the principal axis of the concave reflectorl, is carried by theflatq-j will be reflected as a beam from the parabolic I surface of theconcave reflector 1 on to the adjacent surface of the flat reflector 4from whence it will, to a large extent, be radiated outwardly throughthe outlet orifice A of the structure.

A structure such as described can, as shown, advantageously be housedwithin a rectangular casing or cabinet 8 in such manner that its openside is parallel with and presented to a perforated front wall 8 of thecasing or cabinet, thus causing the flat reflector 4 to assume asubstantially diagonal position across the casing or cabinet, therebyaffording accommodation; for the telephonic receiver 3 between the flatreflector 4 and the wall of the cabinet, the top and bottom of thecabinet conveniently forming the upper and lower boundary walls 6 and 7of the trough or scoop shaped structure. One end of the cabinet 8 isprovided with a hinged door 9 to admit of ready access to the telephonicreceiver 3 for adjustment thereof or for other purpose. Strips 6 and 7of non-resonant material, such for instance as felt, may advantageouslybe arranged between the edges of the reflectors 1 and 4 and rear wall 5and top and bottom walls 6 and 7.

Various modifications of this example can be evolved.

F orinstance, as shown in Fig. 4, the axis 6-00 of the concave reflector1 may be inclined to the axi of the sound conduit 2 and to the flat rearwall 5 and also to the inclined flat reflector 4, so that the soundwaves reflected from the said concave reflector will be directed whollyor partly on to the rear wall 5 which, acting in this case as areflector, will cause them to be reflected through the outlet orifice ofthe structure, the fiat reflector 4 also acting to some extent to assistin the outward diffusion of the said waves.

Fig. 5 shows a similar arrangement to Fig. 4 but in which the inclinedflat reflector 4 is arranged at a greater angle to the axis mw of theconcave reflector 1 than in the arrangement shown in Fig. 4,(practically at right angles to the said axis,) so that the majorportion of the sound waves reflected from the concave reflector 1impinge upon the rear flat reflector 5 and are thence, to a largeextent,reflected on to the inclined flat reflector 4 whence they pass throughthe outlet orifice of the structure.

flector will impinge against the, flat reflector and be reflectedtherefrom as a diffused beam of sound waves through the outlet orificeof the structure.

When the principal focal axis of the concave reflector 1 is inclined tothe axis of the sound conduit 2, as in Figs. 4, 5 and 6, the actualsound emission portion of the conduit may asshown in Fig. 7 at 2*, bedisplaced sideways to coincide with the said axis of the reflector.

The concave reflecting surface 2 instead of being of parabolic shape inhorizontal sec tion, may be of other conic section.

Although the concave reflector 1 in each of the examples hereinbeforedescribed has been assumed tobe straight in cross sect-ion in all planesparallel to one edge 1 thereof (Figs. 2 and 3), it need not always beso,and in some cases it may be a cone. ve surface corresponding to thatswept through by a' curved line rotated about an axis of revolu tion.The curved line may be that of a parabola or any other suitable curve.

Fig. 8shows an arrangement of this kind in which the concave reflector 1has a resides of acabinet to form the upper and lower boundary walls 6and 7 of the scoop-like structure, as in the example shown in F igs. 1,2 and 3, top and bottom walls 6* and 7* maybe combined with the concaveand flat reflectors, to form an independent acoustic amplifier andradiator complete in itself, as shown for example in Figs. 8 and 9, andadapted, if desired, to be mounted within an independent cabinet withits outlet orifice A" arranged opposite the front of the cabinet whichmay be of a perforated or openwork character as shown in Figs. 1 and 2.

When a cabinet is used, a layer 10 (Fig. 3) of sheet material, forinstance textile fabric like silk for example, may be arranged be tweenthe said outlet orifice A and the openwork front of the cabinet. lVhenthe acoustic amplifier and radiator is enclosed within a cabinet, thespace between it and the cabinet, except that containing the telephonicreceiver 3, may be filled with non-sonorous material, asfor instancecotton wool, or other fibrous material, to reduce resonance.

In some cases the construction may be such that the smaller end portionof the conduit 2 extends through one of the horizontal walls 6 or 7 ofthe scoop-like structure, for example through the upper wall 6' andcarries the telephonic receiver 3 outside such wall, as shown forexample in Fig. 10.

What we claim is 1. An acoustic amplifier and radiator comprising aconcavereflector, a sound conduit having its outlet end opposite saidconcave reflector and a flat reflector inclined to the axis of saidconcave reflector and to a sound outlet orifice between them and facingthe reflecting surface of said concave reflector.

2. An acoustic amplifier andradiator comprising a concave reflector, asound conduit having its outletend disposed opposite said concavereflector with its axis coincident with the axis of said concavereflector and a flat reflector inclined to the axes of the concavereflector and sound conduit and facing the reflecting surface of saidconcave reflector.

3. An acoustic amplifier and radiator com prising a concave reflector, asound conduit having its outlet end opposite said concave reflector, aflat reflector, a sound outlet orifice arranged between said reflectors,said flat reflector being inclined to the axis of said concave reflectorand to said sound outlet orifice and facing the reflecting surface ofsaid concave reflector and a telephonic receiver connected to the inletend of said conduit. 7 I

4. An acoustic amplifier and radiator comprising a concave reflector, asound conduit having its outlet end opposite said concave reflector, aflat reflector, and a sound outlet orifice arranged between saidreflectors, said flat reflector being inclined to the axis of saidconcave reflector and to said sound. outlet orifice and facing thereflecting surface of said concave reflector and said conduit extendingthrough said flat reflector.

5. An acoustic amplifier and radiator com prising a concave reflector, aflatreflector inclined to the axis of said concave reflector and facingthe reflecting surface of said concave reflector, walls formedwith saidconcave and flat reflectors, a scoop shapedstructure having a soundout-let orifice at one side, said flat reflector being inclined to theplane of said orifice, and a sound develop ing conduit extending throughsaid structure and having'its outlet orifice disposed opposite saidconcave reflector.

6. An acoustic amplifier and radiator comprising a concave reflector, aflatreflector inclined to the axis of said concave reflector and facingthe reflecting i face of said concave reflector, walls formed ith saidconcave and flatreflectors, a scoop shaped structure having a soundoutlet orifice at one side, said flat reflector being inclined to theplane of said orifice, a sound developing conduit extending through thewall of said structure and having its outlet orifice disposed oppositesaid concave reflector, and a telephonic receiver connected to the inletend of said conduit and located outside said structure.

7. An acoustic amplifier and radiator comprising a concave reflector, aflat reflector inclined to the axis of said concave reflector and facingthe reflecting surface of said concave reflector, flat walls formed withsaid concave and flat reflectors, a scoop shaped structure having arectangularly shaped sound outlet orifice at one side, said flatreflector being inclined to the plane of said orifice, and a sounddevelopingconduit extending through said flat reflector, and having itsoutlet end disposed opposite said concave reflector.

8. An acoustic amplifier and radiator comprising a concave reflector, aflat reflector inclined to the axis of said concave reflector and facingthe reflecting surface of said concave reflector, flat walls, formedwith said concave and flat reflectors, a scoop shaped structure having arectangularly shaped sound outlet orifice at one side, said flat reflector being inclined to the plane of said orifice, a sound developingconduit extending through said flat reflector and havingits outlet enddisposed opposite said concave reflector and a telephonic receiverconnected to the inlet end of said conduit and located behind said flatreflect-or. v

9. An acoustic amplifier and radiator comprising a concave reflector, aflat reflector inclined to the axis of said concave reflector andfacingthe reflecting surface of said concave reflector, a rear wallconnecting the rear ends of said concave and flat reflectors, the frontends of said reflectors being spaced apart to form a sound outletorifice between them, and a sound conduit having its out let enddisposed opposite said concave reflector.

10. An acoustic amplifier and radiator comprising a concave reflector,:a flat reflector inclined to the axis of said concave reflector andfacing the reflecting surface of said concave reflector, a rear Wallconnecting the rear ends of said concave and flat reflectors, the frontend of said reflectors being spaced apart to form a sound outlet-orificeflector inclined to the axis of said concave reflector and facing thereflecting surface of said concave reflector, a rear wall connecting therear ends of said concave and flat reflectors, the front ends of saidreflectors being spaced apart to form a sound outlet orifice betweenthem, walls forming with the said concave and flat reflectors and rearwall, a scoop shaped structure having a sound outlet orifice at one sidethereof, a sound conduit extending through the wall of said structureand having its outlet end disposed opposite said concave reflector and atelephonic receiver connected to the inlet end of said conduit andlocated outside said structure. I

12. An acoustic amplifier and radiator comprising a concave reflector, aflat reflector inclined to the axis of said concave reflector and facingthe reflecting surface of said concave reflector, and a straight soundconduit extending through said flat reflector and having its outlet enddisposed opposite said concave reflector.

13. An acoustic amplifier and radiator comprising a concave reflector, aflat reflector inclined to the axis of said concave reflector and facingthe reflecting surface of said concave reflector, said flat reflect-orhaving its front end spaced away from the front end of said concavereflector so as to form a sound outlet orifice between them, a rear wallconnecting the rear ends of said concave and flat reflectors and astraight sound conduitextending through the flat reflector and havingits outlet end disposed opposite said concave reflector.

14:, An acoustic amplifier and radiator comprising a concave reflector,a flat reflector inclined to the axis of said concave re flector andfacing the reflecting surface of said concave reflector, said flatreflector ha ing its front end spaced away from the front end of saidconcave reflector so as to form a sound outlet orifice between then'i,and a straight sound conduit extending through the flat reflector andhaving its outlet end disposed opposite said concave reflector, the axesof said concave reflector and sound conduit being substantiallycoincident.

15. An acoustic amplifier and radiator comprising a concave reflector, aflat reflector inclined to the axis of said concave reflector and facingthe reflecting surface of said concave reflector, said flat reflectorhaving, its front end spaced. away from the front end of said concavereflector so as to form a sound outlet orifice between them, a rear wallconnecting the rear ends of said con.- cave and flat reflectors and astraight sound conduit extending through the flat reflector and havingits outlet end disposed opposite said concave reflect-or, the axes ofsaid con-- cave reflector and conduit being substantially coincident.

16. An acoustic amplifier and radiator a sound outlet orifice betweenthem, a rearv wall connecting said concave and flat reflectors, wallsarranged to form with the concave and flat reflectors and rear wall ascooplike structure, and a straight sound conduit extending through saidflat reflector and having its outlet disposed opposite said concavereflector.

17. An acoustic amplifier and radiator comprising a cabinet having asound exit at its front side, a concave reflector and a flat reflectorarranged within said cabinet between the top and bottom thereof with theflat reflector inclined to the axis of said concave reflector and to thefront of said cabinet and facing the reflecting surface of said concavereflector, and a sound conduit extending through said flatreflector andhaving its outlet end disposed opposite said concave reflector.

18. An acoustic amplifier and radiator comprising a cabinet having asound exit at its front side, a concave reflector and a flat reflectorarranged within said cabinet between the top and bottom thereof with theflat reflector inclined to the axis of said concave reflector and to thefront of said cabinet and facing the reflecting surface of said concavereflector, non-res0nant material between said reflectors and the top andbottom of said cabinet and a sound conduit extending through said flatreflector and having its outlet end disposed opposite said concavereflector.

19. An acoustic amplifier and radiator comprising a cabinet having asound exit at its front side, a concave reflector a flat reflector and arear wall connecting the rear ends of said reflectors, said reflectorsand rear wall being arranged vertically within said cabinet and betweenthe top and bottom thereof, and with the flat refleet-or inclined to theaxis of said concave reflector and to the front of said cabinet andfacing the reflecting surface of said concave reflector, and a soundconduit extending through said flat reflector and having its outlet enddisposed opposite said concave reflector.

20. An acoustic amplifier and radiator comprising a cabinet having asound exit at its front side, a concave reflector, a flat reflector anda rear wall connecting the rear ends of said reflectors, said reflectorsand rear wall being arrangedvertically within said cabinet and. betweenthe top and bottom thereof, and with the flat reflector inclined to theaxis of said concave reflector and to the frontv of said cabinet andfacing the reflecting surface of said concave reflector, non-resonantmaterial between said reflectors and rear wall and the top and bottom ofsaid. cabinet, and a sound conduit extending through the flat reflectorand having its outlet end disposed opposite said concave reflector.

21. An acoustic amplifier and radiator comprising a cabinet having asound exit at its front side, a concave reflector and a flat reflectorarranged within said cabinet between the top and bottom thereof with theflat reflector inclined to the axis of said concave reflector and to thefront of said cabinet and facing the reflecting surface of said concavereflector, and a straight sound conduit extending through the flatreflector and having its outlet end disposed opposite said concavereflector, the axes of the concave reflector and sound conduit beingsubstantially coincident.

22. An acoustic amplifier and radiator comprising a cabinet having asound exit at its front side and a door at one end, a concave reflectorand a flat reflector arranged within said cabinet between the top andbottom thereof with the flat reflector inclined to the axis of saidconcave reflector and to the front of said cabinet and facing thereflecting surface of said concave reflector, a sound conduit extendingthrough said flat reflector and having its outlet end disposed oppositesaid concave reflector and a telephonic receiver connected to the inletend of said conduit and located within the spaces between the flatreflector and door.

23. An acoustic amplifier and radiator comprising a cabinet having asound exit at its front side and a door at one end, a concave reflector,a flat reflector, and a rear wall connecting the rear ends of said con.-cave and flat reflectors, said reflectors and rear wall being arrangedwithin said cabinet between the top and bottom thereof with the flatreflector inclined to the axis of said concave reflector and to thefront of said cabinet and facing the reflecting surface of said concavereflector, a soundconduit extending through said flat reflector andhaving its outlet end disposed opposite said concave reflector and atelephonic re ceiver connected to the inlet end of said conduit andlocated Within the space between the flat reflector and door.

24. An acousticamplifler and radiator comprising a cabinet having asound exit at the frontand a door at one end, a concave reflector, aflatreflector, and a rear wall connecting the rear ends of said reflectors,said reflectors and rear wall being arranged vertically within saidcabinet between the top and bottom walls thereof with the flat reflectorinclined to the axis of said concave reflector and to the front of saidcabi net, a straight sound conduit extending through the flat reflectorand having its outlet end disposed opposite said concave reflector, theaxes of said'concave reflector and conduit being substantiallycoincident, and a telephonic receiver connected to the inlet end of saidconduit and located between said flat reflector and door.

25. An acoustic amplifier and radiator comprising a cabinet having asound exit at one side, a concave reflector and a flat reflectorarranged Within said cabinet be tween opposite Walls thereof with theflat reflector inclined to the axis of the concave reflector and to thesound exit side of said cabinet and facing the reflecting surface ofsaid concave reflector, and a sound conduit extending into the spacebetween said reflectors and having its outlet opposite said concavereflector.

Signed at London, England,-this eighth day of December, 1926.

MARIA GRAHAM,

Ea -ecatm'm, ALFRED GRAHAM, Executor of Edward A. Graham, Deceased.

